This invention relates to a method of drawing and ironing aluminum and other soft, non-ferrous metals. More particularly, this invention relates to a drawing and ironing method for producing deep drawn aluminum containers, such as beverage containers using an aqueous film forming lubricant.
U.S. Pat. No. 4,262,057 describes a dry film metal drawing compound containing a borate, water and a sodium soap. Although this composition is indicated as being suitable for use in aluminum can drawing, it does not describe compositions similar to those set forth in the instant application.
U.S. Pat. No. 4,260,502 describes a synthetic drawing and ironing lubricant including a low molecular weight polyisobutylene, polyethylene glycol dioleate, a fatty acid soap and a phosphate compound. Again, the compositions set forth in this patent are different from those suitable for use in the method of the present invention and require the presence of a particular low molecular weight polyisobutylene. Furthermore, the method of the present invention has superior lubricating properties compared to the lubricants described in this patent.
U.S. Pat. No. 3,923,671 describes a metal working lubricant which can be used throughout all phases of the metal working process, including as a hydraulic fluid press fluid, stamping fluid, drawing and ironing fluid. This product contains nonionic surfactants and mineral oil. It is desirable for environmental considerations not to utilize mineral oil so as to facilitate easy clean-up and waste disposal.
British Pat. No. 1,459,826 describes a metal working composition, including an amine salt of tall oil, a nonionic surfactant, methyl lardate, biocides, corrosion inhibitor and water. This composition is substantially different than the compositions set forth and used in the method of the present invention.
U.K. Pat. Nos. 1,552,237 and 1,552,238 describe the method of forming hollow coated bodies comprising a step of spreading the coating material on the drum surface of the work piece prior to drawing. The method of the present invention does not require the use of any special apparatus other than that contained in a normal can forming line.
The method of the present invention is particularly desirable in that a single coating composition can be utilized at a relatively low coating weight to quickly and easily form drawn aluminum and other soft metal articles. The method uses an aqueous film former as the lubricant. The method allows beer and beverage containers to be formed at a lower draw force, tooling build-up and having better overall cup suitability. Furthermore, the hold-down pressure which can be achieved in the method of the present invention is substantially higher than those attained using the prior art methods.